1. Field of the Invention
The present invention relates to a tool holding device for use in a printed circuit board processing machine More particularly, the present invention is concerned with a tool holding device which facilitates administration of tools held by the tool holding device.
2. Description of the Related Art
FIGS. 6 and 7 show a known printed circuit board processing machine in which tool holding devices 4 each having a plurality of tool posts 3 are detachably carried by a table 2 on which printed circuit boards 1 are mounted. The tool holding device 4 holds a plurality of tools of different types necessary for processing the printed circuit board 1. The supply of the tools 5 is conducted by preparing the tool holding device 4 holding the tools 5 on the tool posts 3 in a predetermined order and mounting the device 4 on the table 2 of the printed circuit board processing machine. The positions of the tools 5 held by the tool holding device 4 are defined in terms of values of a coordinate system having an origin P on the printed circuit board processing machine.
On the other hand, an NC device for controlling the printed circuit board processing machine stores data concerning the processing conditions such as the speed of rotation of the spindle, feed speed, number of processing cycles till the expiration of the tool life, for each coordinate position with respect to the origin P.
The NC device produces an instruction for exchanging the tool 5 on the spindle 6, in accordance with a predetermined processing sequence, and selects the processing condition corresponding to the coordinate position of the tool 5. As a result, the spindle 6 picks up the required tool 5 and moves to the processing position on the printed circuit board 1, so that the processing is commenced in accordance with the selected processing condition. At the same time, the NC device stores data concerning the state of use of each tool 5.
After the use of the printed circuit board processing device for a predetermined time, the tool holding device 4 is renewed to supply new tools 5. Among the tools 5 on the tool holding device 4 which has been demounted from the printed circuit board processing machine, the tools 5 which have exhausted are replaced with new tools 5.
Each tool holding device 4 holds many tools, e.g., 50 pieces of tool. These tools are used at different frequencies and under different conditions, so that there are many tools which need not be replaced. Some tools 5 have tips of diameters of 1 mm or smaller. Such tools cannot be subjected to grinding for further use. Thus, it is quite impractical and uneconomical to replace all the tools 5 on the tool holding device 4.
It is therefore necessary that the replacement of the tools 5 is conducted in accordance with data concerning the state of the tools 5 read from the NC device. The operation of the printed circuit board processing machine has to be suspended during reading of the data from the NC device. In addition, when the arrangement of the tools 5 on the tool holding device 4 is changed, it is necessary to update the data concerning the processing conditions registered in the NC device. As a consequence, the rate of operation of the printed circuit board processing machine is lowered disadvantageously.